Police then shot dead "two assailants" and "are chasing the rest," Xinhua said, without mentioning the number of suspects in the latest violence to rock Xinjiang.

It quoted witnesses as saying that the "violent mobs chopped the victims" on Xingfu Street at about 6:00 p.m.

However, an email sent to RFA by a Uyghur, who did not identify himself, said that the violence was triggered by an insult thrown at a Uyghur youth by three Han Chinese men at the county's market.

A group of youths aged around 18 years attacked the three Han Chinese, resulting in their death, according to the email.

"Armed police then came in and killed 12 Uyghur youths," the email said.

Both the Xinhua account and details contained in the Uyghur email could not be independently confirmed.

RFA contacted the ruling Chinese Communist Party's propaganda department at the county and an official said he did not have any information to provide immediately.

But sources in the area said the entire county was placed under tight security as motor vehicles were checked at road blocks manned by police, who were also screening the county hospital where the injured had been taken.

Xinjiang has been gripped by persistent ethnic tensions between the Muslim Uyghurs and the rapidly growing Han Chinese migrant population.

Uyghurs, who form a distinct, Turkic-speaking minority in Xinjiang, say they are subjected to political control and persecution for opposing Chinese rule in their homeland.

Uyghur groups use “East Turkestan” to refer to the Xinjiang region, which twice enjoyed short-lived independence from China during the 1930s and 40s.

Enhanced security

Tuesday's violence came amid enhanced security ahead of the National People's Congress (NPC), the country's parliament, annual session opening next week and the ruling Chinese Communist Party leadership transition meeting later this year.

Authorities in Xinjiang's western border prefecture of Aksu detained 103 people during raids that formed part of a nationwide "stability" drive ahead of the meetings, according to the Kunlun official news website.

Regional government departments were implementing an "education, propaganda, walkabout and cleanup" operation, with more than 100 potential security flashpoints being targeted during the latest round of "strike hard" anti-crime campaigns.

The authorities had confiscated materials advertising a "holy war" by Uyghurs, as well as "subversive" literature, it said.

The campaigns have also encompassed widespread forcible "re-education" of local Muslims, according to Dilxat Raxit, spokesman for the Munich-based World Uyghur Congress.

"More than 2,000 people have been subjected to forced re-education and fines that range from 50 yuan to 5,000 yuan (U.S. $8 to $800)," he said.

"Among them were more than 600 women and children."

He said local authorities had issued a notice requiring any ethnic minority Uyghurs entering Aksu to register with police and obtain a certificate of "no crimes committed," though no such requirement exists for China's majority Han Chinese population.

The raids had also focused on mosques and nearby shops in the Aksu region, where authorities had confiscated large amounts of religious literature and DVDs, Raxit said.

"Actually, the campaign against religious activities has spread across the whole of Xinjiang," he said. "In Urumqi, there are police waiting at the railway station and the racetracks and carrying out checks on a residential community at Lengkushan."

"Anyone they think looks suspicious is being stopped and searched," Raxit said, adding that large numbers of "illegal" religious DVDs and publications had been confiscated in Kashgar, in the region's south.

Official denial

An official who answered the phone at the Aksu prefectural religious affairs bureau denied that more than 100 Uyghurs had been detained there.

Calls to the local police department were re-routed to the state security police branch, where a person answering the phone said it was a wrong number.

An employee who answered the phone at a neighborhood committee office in Aksu city said the clampdown was common knowledge, and that no one was now allowed to hold religious meetings or ceremonies in their own homes.

"This isn't just a recent thing; we have always carried out strict searches," she said. "This is an ethnic minority region, and a region of religious belief."

"Wherever you are, they will ferret out illegal religious activities," the employee said.

Meanwhile, in the regional capital of Urumqi, a resident surnamed Zhang said that police had been signing security contracts with business owners since last month and putting up notices in shops, warning people of the additional security measures and searches for "unstable elements."

"If you are renting out rooms, then you have a responsibility to ensure that guests don't engage in any illegal activities in them," Zhang said. "There was an open letter calling on people to inform, and encouraging people to engage in online surveillance and so on."

Last year, Beijing ramped up security before and during for the five-day China-Eurasia Expo trade fair in Urumqi. The added security measures came in the wake of separate attacks in the Silk Road cities of Kashgar and Hotan that killed more than 30 people in July.

Reported by RFA's Uyghur service and Hai Nan for RFA's Cantonese service. Translated by Dolkun Kamberi and Luisetta Mudie. Written in English by Luisetta Mudie and Parameswaran Ponnudurai.